Stabilizing carbon tetrachloride



' Poul Sr lirolli r, it

' Niagara Emeltihe, 'fio w l The ele ant se en relies to em t-ems i i -f h1bnaet common inhibiting ogent-iorit; -,sne a, method of inhibiting the-corrosiveiactionwoi 1 carbon tetrachloride on.tenets-ls. t

' Inm'any proessesitisnecessery tousecorhon tetrachloride in inetalcontainers. -Aslanifexam "ple theory 'cleaning ert isreferred toinliilustre- *tion of the use 1 of the invention, because it has under present economic w conditions,- provides for recovery of used cleening agcnt by distillation; It has-been found that the commonfmetals used for eppdiatus, suchas steel, copper, brass encileachere subject tocorrosion by carbon tetrachloride as it is used for example in'dry oleening; Apparatus for distillation emireoovczw, for

" storage of distllledmeteriol 'islilrewisesubjectto I Jcorrosion,and.at-aimuch'msterroteioeceuse of: the increased temperature? g v The present imzention isbesed upon dieeovery oithe causes bihbrroslomrand the introduction;

of suitable agent-or egentsto inhibit the @9130.- sion. i t

t given metal.

coveryoi theinhibltedmixture. g A further objeotis theuse of 3a, volatile iiriloibi-gtor which is capable of distilling over 1 with the carbontetrachlorideflin the normal procedure of distilling the latter; so that special' attention to dlsmlatlon is not reqmred assuring plenetion heoeuse the metelo whiehere suhject "easily'to con-mien by hydrochloric eoloere the xtlon oi the.inhihiting suhstancei t A particular object-of the invention is the ofan ester of an alcohol endcan organic acid or a mixture of themasinhibiting substance for the corrosion oi copper. l Intheiollowlng 4 *encountrecl in the cleaning field but it is, t to be'understood that the invention is not limited in applicationtosuch fleld,"a'.nd that itis useful Q extraction processesfor-iets, oils, waxes end:

' thelike. Detaileci examples are givemciting. spea- 0 cifioj metal, and specific inhibitors, but it isto be understood' that the invention is notto be con- -sidereda's limited to the specific disclosures.

Such other'uses of the e 1' *thereoL are contemplate'dpas" !all within fi -scopeot the accompanying 1 invention, and variations accelerated os corrosion occurs. i fore e, self-catalyzing efieot. For example when equallayers-of water endear-hon tetrachloride hours:

one object or the nvention isthe addition of an inl'iibitinge'gent or mixture of such agents to. v cerho'n tetrachloride tominimize its corrosive-es -tion m jcertain'uses thereof in conteotwith a,

description of the intention t i reference is made by wayloiexample to conditions ,therein, which contain oerhem 3.0% oi moisture. 555

' e invention isbesed upon the discovery that corrosion of metal by carbon tetrachloride cc-t uid phase of carbon tetrachloride; By careful study Iheve discovered that pure water andpure qrcarhon tetrachloride placed in contact-with metgreat and particular. merit-in thet rflelcl. Annat retus for cleaning with carbon tetrachloride;

el have together it corrosive effect which is at first a "minimum; it been ascertained par- 1 'ticulerly with: copper that the corrosive efiect is It has there- Vere refluxed at theboiling point of the carbon 15 tetrachloride, endvcopper is in contact with the two liquid nheses and the vapor phase, the cor- =rosionhos been found, under the particular con.-

ditions tube at the following average rates per 24:

2G I v 7,; Milligrams per soJdlecimeter "yfgpgr phrase 3Q Carbon tetrechloriole whose"; .i i so Water tphosenu e reset "rete'oi corrosion; heemcieerly ohservei 25 to increase as comer chloride is termed in the liouid'nlies'e,

The mitiei'ceuse o2 con-once is suggested to he the iormntionoi hyairoehlcric eciti he" at rem mm limited degree of hydrolysis oi'the carbon tetrua chloridehit eetion oi? Weter. There is e tendency to hyiysis end this e he iiizeneoi toe, strained condition. It is helieveti that the metel suriece relieves strein lond eccor z: 35

min me he considered a s cat for the-hydrolysis. This is helleveu to he the oorrect ex- "rnetelswhich are corroded hy wetereno cerhon m tetrachloride. fil'he'eeirl is collected by the outer as it is formed;- It then is active the netal, forming in the cone oi copper, copper chloe ride in solution, eppeereto hove o cec ,efleot to n hydrolysis cl form more eciol,

end henoemore corrosion enol hence more cotelyzer. It is of course not known precisely to whet extent the here metel, or my omcle oreutphiue the possibility is not at ell, remote.

In many erts perticuinrly zirycleening. water is unevoiciohly present in oer-hen tetrachloride. It may be acquired by e air-dried fabrics film thereon, meyinitiellw act es e ceteiyeer, but

This may be replaced by carbon tetrachloride, forcing water from the fabric into the carbon tetrachloride. I am not concerned particularly with any special. catalyzer, particularly in dry cleaning, because it is unavoidable that impurities are introduced, such as phosphorus from matches which may bein pockets, rust and all kindsof dirt, and many of these may be catalyzers. i V

In experimenting with copper, as a suitable metal for dry cleaning apparatus I have found that esters may be added in varying amounts singly or in admixture to carbon tetrachloride, so that in the presence of water the corrosive action is greatly reduced. I have used formates,

acetates, propionates, benzoates, crotonates and salicylates of methyl, ethyl and propyl alcohols with advantage. Varying percentages from large to small are effective to give an inhibiting -action. a

In order to illustrate the improvement, or the inhibiting action, I have made comparative tests under fixed conditions which give relative measures-of the efiiciency. By using equal layers of water and carbon tetrachloride containing a measured percentage by volume of. inhibitor (based on the volume of the carbon tetrachloride employed), and refluxing at the normal boiling point of carbon tetrachloride for at least 24 hours (in contact with metal at the water layer) the extent of corrosion may be determined. wTests have been made of refluxing for seven days. For

convenience, the milligrams of metal dissolved persq. dm. per unit of 24 hours," while in test, are referred to as the corrosion figure. With no inhibitor it may be found to be 3766 mil1i-' grams per square decimeter per 24 hours while in test. It will be noted that'this figure varies from one given above, but this merely indicates that the factors were different, and that the results are merely relative and not absolute. If-

these figures are properly weighted in accordance with the areas of metal exposed to the 3 phases, a consistency can be shown. It is also apparent that the area of metal exposed has some relation to the volume of liquid present. However, when 5% of methyl propionate is added, the corrosion figure is reduced from 3766 tofrom 1200 to 1500. When 5% of n-propyl formate is used, the corrosion figure has been foundto be 1200 to 1500. When 5% of ethyl acetate is used, the corrosion figure has been high, at 3509. But when 36% of effective than methylfpropionate.

In selecting an inhibitor'I prefer a volatile one,

but this is of course not essential in the broadest aspects of the invention. In selecting a volatile one I prefer one which volatilizes with the carbon tetrachloride in distillation for recovery of an in-.

hibited mixture. Inhibitors which boil from C. or 18 F. on either side of the boiling point of carbon tetrachloride (77 C.) are suitable. Ethyl acetate has approximately the same boiling point as carbon tetrachloride.

I have used the materials effectively in concentrations as low as .2% by volume and up to and above 5% by volume, and find that the lower quantities are as effective and sometimes apparently more effective than a larger quantity, such as 5%. Thefollowing table-gives materials,

' the lowest quantity tested, and a corrosion figure therefor. i

Percent by Corrosion Mam volume figure No inhibi 3706 Normal propyl iormate 0. 14 1606 Ethyl! 0. 26 2060 Met y] propionate 0. 21 1622 Ethyl crotonatc 0. 21 1656 Ethyl benzoate 0. 28 1974 Methyl salioy 0. 56 3260 The character of results from numerous studies is suggestive of the possibility that the inhibitor acts as a film at the metal surface, possibly being selectively adsorbed by it from the body of the liquid. The fact that small quantities are as effective'as larger quantities supports this theory.

Such an adsorbed film would insulate the carbon tetrachloride from the metal and minimize catalytic effects of the metal. Such a theory indicates that the effects will be dependent both on the metal and the'inhibitor, andgthat the inhibitor must be chosen with respect for the metal exposed. This is in accordance withexperimental findings that an inhibitor which is suitable for one metal is not suitable for all metals. The film theory would account for lack of great improvement in increasing. the quantity of inhibitor, which is likewise consistent with experimental findings. It is not however intended to limit the invention functioning. V

Itis to be understood that no upper limit of concentration is herein defined. Very much larger quantities have been used, for example, 36% by volume of ethyl acetate for copper, with a corrosion figure of 234. Because the inhibitors are ordinarily more expensive'than the carbon tetrachloride base, it is highly advantageous that very small quantities are practically eifective. In like manner no lower limit is defined. According to the projected theory of the action, very much smaller quantities than .2 would sufiice, but a sufiicient excess is deemed desirable'to insure against accidental reduction'of the concentration to a point below some critical point, which would vary with conditions, if the film theory is correct.

For all practical purposes it may be considered that 5% is a safe commercialupper limit for an inhibited mixture which is intended for use in dry cleaning with subsequent recovery operations. For the simple purpose of exerting an inhibiting function, a small but appreciable, quantity under 1% is considered sufiicient. Hence, for practical purposes, some of the claims'define the invention within these limits,'without', however, limiting th scope as defined by otherclaims.

I have also observed thatan inhibitor which is specific for one metal may be an accelerator forcorrosion of other metal. It is therefore a matter of experiment with specific metals and specific materials to determine which combinations have thedesired advantage. I canndt of course run through tests with all vtheavailable metals and all the available materials which might be inhibitors. Therefore I consider that the invention hereinis the act of adding a proper to or by this theory of'its I "2,002,168 r 3 soluble inhibiting agent to carbon tetrachloride, corrosive action of carbon tetrachloride in the in adding one which "is volatile, and in adding presence 01 water which comprises adding to the one which is volatile with the carbon tetrachloride carbon tetrachloride ethyl acetate.

in distillation thereon '2. Carbontetrachloride containing ethyl ace 5'Iclaim: g t 1 V- 1. The method of protectingcopper from the PAUL S. BRAHIIER. 

